The most important thing with trees is to make sure they are watered, as needed, up until the ground freezes. Winter winds strip moisture from bare branches. A tree that is water stressed going into winter is a problem. The rest is up to Mother Nature. If you only recently planted your trees, mulch the ground over the rootball with 4 inches of straw, chopped leaves or wood mulch. Just don't let the mulch touch the bark. Leave a 2-3 inch gap. The other issue for you is how to protect the saplings from hungry wildlife. Mice and rabbits will nibble on young bark to say nothing of deer. Constructing a cage with chicken wire or hardware cloth and stakes or PVC pipe is fairly simple. Just make it tall enough to keep deer from eating your central leader. Here is an article with more info. https://www.extension.purdue.edu/extmedia/fnr/fnr-484-w.pdf
Check with your state Extension office for advice specific to your region. Search online for [your state] Extension Service.